Synthetic grass sports surfaces are well known. These surfaces are becoming increasingly popular as replacements for natural grass surfaces in stadiums, playgrounds, golf driving ranges, and a variety of other facilities. The synthetic grass surfaces stand up to wear much better than the natural grass surfaces, do not require as much maintenance, and can be used in partially or fully enclosed stadiums where natural grass cannot typically be grown.
Most synthetic grass surfaces comprise rows of strips or ribbons of synthetic grass-like material, extending vertically from a backing mat with particulate material infill (“infill”) in between the ribbons on the mat. One or more layers of aggregate material are introduced between the backing mat and on top of a smoothed and compacted subgrade. The grass surfaces are usually sloped, and typically utilize drainage systems, to facilitate drainage resulting from rainstorms or other events.
The infill usually comprises sand, as shown by way of example in U.S. Pat. No. 3,995,079 and U.S. Pat. No. 4,389,435, both to Haas, Jr. More recently, the particulate matter can also comprise a mixture of sand and other materials, including rubber infill, as shown, for example, in U.S. Pat. No. 6,338,885 to Prevost, or entire rubber infill systems, such as those disclosed in U.S. Pat. No. 5,976,645 to Daluise et al. In these systems, the particulate matter provides resiliency to the synthetic grass surfaces and adds weight to hold down the backing material, thus helping to ensure that the strips of synthetic grass do not move or shift during play.
The use of infill in synthetic turf fields, especially infill that includes resilient materials such as rubber, has raised environmental concerns as to the effect of such materials, or chemical components of such materials, leeching into water tables for turf fields utilizing the ground for drainage. For turf fields having drainage systems incorporated in their design that substantially prevent water runoff from reaching the water tables, there are still environmental concerns with allowing these materials to enter storm or sewer drains.